Wind power is considered one of the cleanest, most environmentally friendly energy sources presently available, and wind turbines have gained increased attention in this regard. A modern wind turbine typically includes a tower, generator, gearbox, nacelle, and one or more rotor blades. The rotor blades capture kinetic energy from wind using known foil principles and transmit the kinetic energy through rotational energy to turn a shaft coupling the rotor blades to a gearbox, or if a gearbox is not used, directly to the generator. The generator then converts the mechanical energy to electrical energy that may be deployed to a utility grid.
Conventional rotor blades typically include a shell formed from two shell halves coupled together along corresponding edges of the rotor blade. The shell halves and, thus, the shell are relatively lightweight and have insufficient structural properties (e.g., stiffness and strength) to withstand the bending moments and other loads exerted on the rotor bade during operation. In addition, the size, shape, and weight of rotor blades are factors that contribute to energy efficiencies of wind turbines. For example, an increase in rotor blade size increases the energy production of a wind turbine, while a decrease in weight also furthers the efficiency of a wind turbine. As rotor blade sizes grow, extra attention needs to be given to the structural integrity of the rotor blades. Thus, it is known in the art to reinforce the shell using a spar assembly consisting of a pair of opposed spar caps and a shear web extending perpendicularly between the opposed spar caps. This conventional spar configuration generally provides a rotor blade with a relatively high, constant stiffness. However, the spar caps are typically large (e.g. extending the span of the rotor blade) and difficult to install.
In addition, as the size of the rotor blades increases, so do the respective costs of manufacturing, transporting, and assembling of the wind turbines. One known strategy for reducing the costs of pre-forming, transporting, and erecting wind turbines with rotor blades of increasing sizes is to manufacture the rotor blades in blade segments. The blade segments may be assembled to form the rotor blade after, for example, the individual blade segments are transported to an erection location. However, known joint designs and assembly processes may have a variety of disadvantages. For example, many joint designs include a scarf joint having opposing tapered ends which are then fitted together. The scarf joints, however, involve a time consuming and expensive scarfing operation that must be completed for the spar caps of the existing blade before the blade segments can be joined together.
Blade tip extensions are also known in the art for increasing the length of rotor blades. Such extensions are typically installed by cutting a rotor blade in half and inserting a middle portion between the two halves so as to extend the rotor blade. Similar to the blade segments discussed above, blade tip extensions experience similar disadvantages in known joint designs.
Accordingly, there is a need for an improved spar assembly that addresses the aforementioned issues.